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Movement disorders are defined as either a loss or poverty (akinesia) or slowness (bradykinesia) of movement that is not associated with weakness or an excess of abnormal involuntary movements. Based on this, movement disorders are classified as either hypokinetic (Parkinsonism) or hyperkinetic (tremor, dystonia, chorea, tics, myoclonus). Movement disorders are generally caused by abnormalities in basal ganglia and their connections. The basal ganglia are that group of gray matter nuclei lying deep within the cerebral hemispheres (caudate, putamen, and pallidum), the diencephalon (subthalamic nucleus), and the mesencephalon (substantia nigra). The causes of many movement disorders remain unknown, in others various causes have been identified ranging from environmental toxins, genetic causes, medications, metabolic disorders, structural lesions, neurodegenerative causes, infectious, postinfectious causes, and autoimmune and psychogenic causes. More recent genetic, biochemical, and functional imagine advances have provided additional information about the pathophysiology and etiology of some movement disorders. Many diseases have now been localized to a specific gene (PD, dystonia, ataxia, paroxysmal dyskinesia, etc); several inherited movement disorders are due to expanded repeats of the trinucleotide cytosine-adenosine-quanosine (CAG) such as Huntington disease, some spinocerebellar ataxias (SCAs), and Dentatorubral and Pallidoluysian Atrophy (DRPLA).

Movement disorders must be seen, because description of them by the parents or patient might be vague and will not lead to a proper diagnosis. Children also manifest a variety of intriguing physiologic and developmental abnormalities that await proper classification, and only the experienced movement disorders observer can distinguish those from movement disorders.

Many abnormal movement disorders are paroxysmal or at least intermittent; they can be induced by sleep, emotional upset, movement, or other triggering factors. The physician needs to ask what are triggering factors and what makes the movement better and worse, if there is fluctuation of symptoms during the day, and if there are any associated features (ie, loss of consciousness or awareness). Many paroxysmal movements in pediatric population are associated with epilepsy, and this has to be to exclude by appropriate investigation (see Chapter 557). Movement disorders may be classified as follows:

  • Hyperkinetic movement disorders
  • Chorea and athetosis
  • Dystonia
  • Tremor
  • Myoclonus
  • Tics and Tourette syndrome
  • Stereotypy
  • Hypokinetic movement disorders
  • Parkinsonism

Chorea and Athetosis

  • Chorea is a combination of fluid or jerky movement affecting any part of the body; chorea can resemble a dance (from Greek word), and movements are repetitive but not rhythmic or stereotyped. Patients with chorea appear restless.
  • Athetosis is a slow, writhing movement of the limbs that may occur alone but is often associated with chorea (choreoathetosis).
  • Ballismus is a high-amplitude, violent flinging of a limb from the shoulder or pelvis and is considered to be an extreme form of chorea.

Common causes of chorea are listed in Table 566-1.

Table 566-1. Causes of Chorea

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